Self servo writing disk controller and methods for use therewith

ABSTRACT

A self servo writing disk controller detects a plurality of spiral sync marks and a plurality of spiral bursts corresponding to one of a plurality of servo spirals from a read signal from the read/write head. A timing reference signal is generated based on timing of at least one of the plurality of the spiral sync marks. A position error signal is generated based on timing of at least one of the plurality of spiral sync marks and a magnitude of at least one of a plurality of spiral bursts. The timing reference signal and the position error signal are used by the disk drive for timing and positioning in self writing initial servo wedges to the disk.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. 120 as acontinuation of the copending application having Ser. No. 11/521,040,entitled SELF SERVO WRITING DISK CONTROLLER AND METHODS FOR USETHEREWITH, filed on Sep. 14, 2006 which claims priority to U.S.Provisional Patent Application Ser. No. 60/813,194, filed Jun. 12, 2006,both of which are incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to the self servo writing disk drives andrelated methods.

2. Description of Related Art

As is known, many varieties of disk drives, such as magnetic disk drivesare used to provide data storage for a host device, either directly, orthrough a network such as a storage area network (SAN) or networkattached storage (NAS). Typical host devices include stand alonecomputer systems such as a desktop or laptop computer, enterprisestorage devices such as servers, storage arrays such as a redundantarray of independent disks (RAID) arrays, storage routers, storageswitches and storage directors, and other consumer devices such as videogame systems and digital video recorders. These devices provide highstorage capacity in a cost effective manner.

As a magnetic hard drive is manufactured, portions of the disk areprerecorded at the factory. A plurality of servo spirals are written tothe disk in spiral patterns that begin from the innermost to theoutermost writeable section of the disk. In addition, a plurality ofservo wedges are written to the disk contained in radial segments aboutthe disk. For each track on the disk, each servo wedge contains a servofield that is recorded with a preamble, a synchronization mark and servodata. Examples of servo data include a servo address mark, wedge number,track number, and burst data used by a disk controller to control therotation of the disk and the position of the read/write heads of thedisk drive. Given the need for highly accurate positioning, these servospirals and servo wedges are traditionally recorded on the disk using aservo writer. Given a desire to minimize the use of the servo writer,certain self servo writing disk drives write the servo spirals and onlya certain number of seed servo wedges, with the remaining servo wedgesbeing written to the disk by the disk drive itself.

A sizable market has developed for these devices and the price per unitof storage has steadily dropped. Modern host devices are provided withgreater storage capacity at reduced cost, compared with devices thatwhere manufactured a few years earlier. The need exists for provide harddrives that can be manufactured efficiently on a mass scale with highaccuracy.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 presents a pictorial representation of a disk drive unit 100 inaccordance with an embodiment of the present invention.

FIG. 2 presents a block diagram representation of a disk controller 130in accordance with an embodiment of the present invention.

FIG. 3 presents a block diagram representation of a disk controller 275in accordance with an embodiment of the present invention.

FIG. 4 presents a pictorial representation of the reading of a servospiral 160 by a read head 162 in accordance with an embodiment of thepresent invention.

FIG. 5 presents a block diagram representation of the contents of servospiral 160 in accordance with an embodiment of the present invention.

FIG. 6 presents a graphical representation of a read signal generated byreading a portion of a servo spiral in accordance with an embodiment ofthe present invention.

FIG. 7 presents a graphical diagram representation of a burst marktiming window 340 and spiral sync mark timing window 342 in accordancewith an embodiment of the present invention.

FIG. 8 presents a block diagram representation of a spiral sync markdetector 142 in accordance with an embodiment of the present invention.

FIG. 9 presents a graphical representation of a plurality ofinterpolated read samples 330 in accordance with an embodiment of thepresent invention.

FIG. 10 presents a graphical representation of the operation ofmagnitude estimation module 306 in accordance with an embodiment of thepresent invention.

FIG. 11 presents a block diagram representation of a timing generator110 in accordance with an embodiment of the present invention.

FIG. 12 presents a pictorial representation of a disk 200 having aplurality of servo wedges and a plurality of tracks in accordance withan embodiment of the present invention.

FIG. 13 presents a block diagram representation of a servo field 210 inaccordance with an embodiment of the present invention.

FIG. 14 presents a pictorial representation of a handheld audio unit 51in accordance with an embodiment of the present invention.

FIG. 15 presents a pictorial representation of a computer 52 inaccordance with an embodiment of the present invention.

FIG. 16 presents a pictorial representation of a wireless communicationdevice 53 in accordance with an embodiment of the present invention.

FIG. 17 presents a pictorial representation of a personal digitalassistant 54 in accordance with an embodiment of the present invention.

FIG. 18 presents a pictorial representation of a laptop computer 55 inaccordance with an embodiment of the present invention.

FIG. 19 presents a flowchart representation of a method in accordancewith an embodiment of the present invention.

FIG. 20 presents a flowchart representation of a method in accordancewith an embodiment of the present invention.

SUMMARY OF THE INVENTION

The present invention sets forth a self servo writing disk controllerand methods for use therewith substantially as shown in and/or describedin connection with at least one of the figures, as set forth morecompletely in the claims that follow.

DETAILED DESCRIPTION OF THE INVENTION INCLUDING THE PRESENTLY PREFERREDEMBODIMENTS

FIG. 1 presents a pictorial representation of a disk drive unit 100 inaccordance with an embodiment of the present invention. In particular,disk drive unit 100 includes a disk 102 that is rotated by a servo motor(not specifically shown) at a velocity such as 3600 revolutions perminute (RPM), 4200 RPM, 4800 RPM, 5,400 RPM, 7,200 RPM, 10,000 RPM,15,000 RPM, however, other velocities including greater or lesservelocities may likewise be used, depending on the particular applicationand implementation in a host device. In an embodiment of the presentinvention, disk 102 can be a magnetic disk that stores information asmagnetic field changes on some type of magnetic medium. The medium canbe a rigid or nonrigid, removable or nonremovable, that consists of oris coated with magnetic material.

Disk drive unit 100 further includes one or more read/write heads 104that are coupled to arm 106 that is moved by actuator 108 over thesurface of the disk 102 either by translation, rotation or both. In anembodiment of the present invention, the read/write heads 104 include awrite element, such as a monopole write element that writes data on thedisk with perpendicular magnetic recording (PMR), longitudinal magneticrecording (LMR) or other recording orientation. This allows for greaterrecording density and greater storage capacity for the drive. However,other recording configurations can likewise be used within the broadscope of the present invention.

A disk controller 130 is included for controlling the read and writeoperations to and from the drive, for controlling the speed of the servomotor and the motion of actuator 108, and for providing an interface toand from the host device.

When disk drive 100 is manufactured, a servo writer is used to write aplurality of servo spirals on the disk 102. When the disk 102 is theninstalled in the drive, disk controller 130 runs a self servo writerroutine that determines position and timing information by reading theservo spirals and that writes the servo wedges on the disk. Inparticular, disk controller 130 detects a plurality of spiral sync marksand a plurality of spiral bursts corresponding to one of a plurality ofservo spirals from a read signal from the read/write head. A timingreference signal is generated based on timing of at least one of theplurality of the spiral sync marks. A position error signal is generatedbased on timing of at least one of the plurality of spiral sync marksand a magnitude of at least one of a plurality of spiral bursts. Thetiming reference signal and the position error signal are used by thedisk drive 100 for timing and positioning in self writing initial servowedges to the disk 102. The present invention includes several benefitsthat will be apparent to one skilled in the art based on the disclosurethat follows. In particular, the present invention detects spiral syncmarks and burst magnitude during start up that enables simultaneousand/or contemporaneous timing locking and position locking.

Further details including several embodiments of the present inventionwill be discussed in conjunction with the figures that follow.

FIG. 2 presents a block diagram representation of a disk controller 130in accordance with an embodiment of the present invention. Inparticular, disk controller 130 includes a read/write channel 140 forreading and writing data to and from disk 102 through read/write heads104.

Disk formatter 125 is included for controlling the formatting of dataand provides clock signals and other timing signals that control theflow of the data written to, and data read from disk 102. In particular,read/write channel 140 is operably coupled to the read/write head toread the servo data 118 from the disk. Servo formatter 120 is operablycoupled to the read/write channel 140 to generate timing and positionsignals 116 based on the servo data 118 that is read, so that devicecontrollers 105 can control the operation of the plurality of drivedevices based on the timing and position signals 116.

In an embodiment of the present invention, the read/write channelincludes a repetition decoder, majority logic detection, matched filter,correlator, integrator and/or maximum likelihood detector for decodinggray-coded track identification data 216 and the burst data 218. Thisservo data is used to extract the track number, by gray decoding thetrack identification data. In addition, subtrack position is determinedbased on the relative magnitudes of A, B, C, and D data bursts 218.Further details regarding the subtrack control and positioning arepresented in U.S. Pat. No. 6,108,151, Sampled Amplitude Read Channel forReading User Data and Embedded Servo Data from a Magnetic Medium, filedon Apr. 25, 1997.

In addition, the servo formatter 120 generates timing information basedon the detected servo address mark 220 for use by device controllers 105for controlling the actuator 108 and spindle motor, and optionally forgenerating other timing information used by disk formatter 125 andread/write channel 140 in timing of disk write operations. Furtherdetails regarding the use of servo address mark 220 in such timingoperations are presented in pending U.S. patent applications Diskcontroller and methods for use therewith, having Ser. No. 11/311,725;Media event timer and methods for use therewith, having Ser. No.11/311,727; and Read/write timing generator and methods for usetherewith, having Ser. No. 11/311,726.

Host interface 150 receives read and write commands from host device 50and transmits data read from disk 102 along with other controlinformation in accordance with a host interface protocol. In anembodiment of the present invention the host interface protocol caninclude, SCSI, SATA, enhanced integrated drive electronics (EIDE), orany number of other host interface protocols, either open or proprietarythat can be used for this purpose.

Disk controller 130 further includes a processing module 132 and memorymodule 134. Processing module 132 can be implemented using one or moremicroprocessors, micro-controllers, digital signal processors,microcomputers, central processing units, field programmable gatearrays, programmable logic devices, state machines, logic circuits,analog circuits, digital circuits, and/or any devices that manipulatessignal (analog and/or digital) based on operational instructions thatare stored in memory module 134. When processing module 132 isimplemented with two or more devices, each device can perform the samesteps, processes or functions in order to provide fault tolerance orredundancy. Alternatively, the function, steps and processes performedby processing module 132 can be split between different devices toprovide greater computational speed and/or efficiency.

Memory module 134 may be a single memory device or a plurality of memorydevices. Such a memory device may be a read-only memory, random accessmemory, volatile memory, non-volatile memory, static random accessmemory (SRAM), dynamic random access memory (DRAM), flash memory, cachememory, and/or any device that stores digital information. Note thatwhen the processing module 132 implements one or more of its functionsvia a state machine, analog circuitry, digital circuitry, and/or logiccircuitry, the memory module 134 storing the corresponding operationalinstructions may be embedded within, or external to, the circuitrycomprising the state machine, analog circuitry, digital circuitry,and/or logic circuitry. Further note that, the memory module 134 stores,and the processing module 132 executes, operational instructions thatcan correspond to one or more of the steps or a process, method and/orfunction illustrated herein.

Disk controller 130 includes a plurality of modules, in particular,device controllers 105, processing module 132, memory module 134,read/write channel 140, disk formatter 125, servo formatter 120 and hostinterface 150 that are interconnected via buses 136 and 137. Each ofthese modules can be implemented in hardware, firmware, software or acombination thereof, in accordance with the broad scope of the presentinvention. While a particular bus architecture is shown in FIG. 2 withbuses 136 and 137, alternative bus architectures that include either asingle bus configuration or additional data buses, further connectivity,such as direct connectivity between the various modules, are likewisepossible to implement the features and functions included in the variousembodiments of the present invention.

In an embodiment of the present invention, one or more modules of diskcontroller 130 are implemented as part of a system on a chip integratedcircuit. In an embodiment of the present invention, this system on achip integrated circuit includes a digital portion that can includeadditional modules such as protocol converters, linear block codeencoding and decoding modules, etc., and an analog portion that includesadditional modules, such as a power supply, disk drive motor amplifier,disk speed monitor, read amplifiers, etc. In a further embodiment of thepresent invention, the various functions and features of disk controller130 are implemented in a plurality of integrated circuit devices thatcommunicate and combine to perform the functionality of disk controller130. Additional details regarding the self servo writing functionalityof disk controller 130 are presented in conjunction with FIG. 3 thatfollows.

FIG. 3 presents a block diagram representation of a disk controller 275in accordance with an embodiment of the present invention. Inparticular, disk controller 275 is a self servo writing disk controllerfor use in a disk drive, such as disk drive 100, having at least oneread/write head for reading data from and writing data to a disk, suchas disk 102.

Read/write channel 140 includes a spiral detection module 250 thatanalyzes a read signal 310 from the read/write head, detects a pluralityof spiral sync marks and a plurality of spiral bursts corresponding toone of a plurality of servo spirals written on the disk, and thatgenerates a timing reference signal 262 based on timing of at least oneof the plurality of the spiral sync marks and a position error signal260 based on timing of at least one of the plurality of spiral syncmarks and a magnitude of at least one of the plurality of spiral bursts.Timing generator 110 generates a clock signal 126 and media eventssignal that includes at least one media event trigger that is based onthe timing reference signal 262.

Device controller 266 controls at least one drive device of disk drive100, (such as to control the position of the read/write head, thevelocity of the disk 102, etc.) via device drive signals 264, based onthe position error signal. Servo data generation module 252 generatesservo data 254 corresponding to a plurality of servo wedges of the disk252. Servo write module 256 generates servo wedge write signals 258 forwriting the plurality of servo wedges on the disk based on the clocksignal and the at least one media event trigger of media events signal124.

In operation in accordance with an embodiment of the present invention,the disk controller 275 self writes the servo wedges on the disk, basedonly on the servo spirals. In this fashion, the time that disk 102 is onthe servo writer in the factory can potentially be reduced, since onlythe servo spirals need to be written.

In an embodiment of the present invention, disk controller 275 isimplemented using the architecture set forth in disk controller 130discussed in conjunction with FIG. 2. In particular, the devicecontroller 266 is implemented as one or more of the device controllers105, and the spiral detection module 250, timing generator 110, servowrite module 256 and the servo data generation module 252 areimplemented as either portions of, or adjuncts to, the read/writechannel 140, servo formatter 120 and disk formatter 125 of diskcontroller 130. Consequently, each of these elements can be implementedas modules of disk controller 130 in software, firmware or hardware,depending on the implementation of disk controller 130.

Further details regarding the possible operation and implementations ofspiral detection module 250 are presented in association with FIGS.4-10. Further details regarding the possible operation andimplementations of timing generator 110 are presented in associationwith FIG. 11. Further details regarding the writing of the servo data254 is presented in association with FIGS. 12-13.

FIG. 4 presents a pictorial representation of the reading of a servospiral 160 by a read head 162 in accordance with an embodiment of thepresent invention. In particular, the disk, such as disk 102, has beenrecorded with a plurality of servo spirals, each spiral traversing aspiral path from the innermost, to the outermost, data area of the disk.In an embodiment of the present invention, 400 servo spirals arerecorded, corresponding to twice the intended number of servo wedges,however, a greater or lesser number of servo spirals, and/or servowedges (with a potentially different relationship between the number ofservo spirals and servo wedges) can otherwise be used.

The reading of a particular portion of a particular servo spiral 160 isillustrated. Read head 162 follows a path along the disk that is boundedby dashed lines 163. Read head 162 initially intersects servo spiral 160at boundary 164 and subsequently passes through boundary 166 afterleaving the area of servo spiral 160. Read head 162 generates a readsignal that initially has a negligible magnitude prior to theintersection because the portions of the disk outside of the servospirals are effectively blank. The intersection of the path of read head162 and servo spiral 160 generates a read signal that grows in magnitudeas the read head 162 intersects a greater portion of boundary 164 andthat decreases in magnitude as the read head 162 intersects a smallerportion of boundary 166. The result is a read signal having an envelopethat ramps upward and then ramps downward.

FIG. 5 presents a block diagram representation of the contents of servospiral 160 in accordance with an embodiment of the present invention. Inparticular, the servo spiral, such as servo spiral 160, is written witha plurality of spiral sync marks (SSMs) 180, 182, 184, and 186 that areseparated by a spiral bursts 170, 172, 174, . . . . While four spiralservo marks and three spiral busts are shown, a single servo spiral,such as servo spiral 160 includes a far greater number of spiral syncmarks and spiral bursts continuously along its path. While the actualnumber of spiral sync marks is dependent upon such factors as the numberof tracks of the disk and the dimensions of the read head 162, thespiral sync mark density is chosen such that when the read head 162traverses the servo spiral 160, a minimum number of spiral sync marks,such as 1, 2, 3, 4, or more are necessarily traversed, regardless of theparticular position of the head.

In an embodiment of the present invention, the spiral sync marks arespecial binary patterns encoded with partial response signaling thatuses wide bi-phase encoding and pulses such as EPR4 pulses. In effect,each peak in a wide bi-phase cell represents a 1 or a 0. Consider thefollowing example:

SSM binary pattern: 0       1       0 SSM Pattern after 1 1 0 0 0 0 1 11 1 0 0 wide biphase encoding: SSM pattern after x x x −2 −1 0 1 2 1 0−1 −2 EPR4:

The servo sync mark (SSM) is an alternating pattern of binary digitsthat is wide biphase encoded and that generates a signal with eitherpositive or negative peaks (−2, 2, −2 . . . ) when read by read head104.

FIG. 6 presents a graphical representation of a read signal generated byreading a portion of a servo spiral in accordance with an embodiment ofthe present invention. In particular, read signal 310 presents a typicaldiamond pattern generated by a read head, such as read head 162traversing a potion of a servo spiral such as servo spiral 160. Asdiscussed in conjunction with FIGS. 4 and 5, spiral bursts 332, 334 and336 generate sinusoidal responses at a first frequency and spiral syncmarks 322, 324, and 326, generate sinusoidal responses at a secondfrequency, and read signal 310 has an envelope 330 that ramps upward andthen ramps downward.

In an embodiment of the present invention, spiral detection module 250compares the magnitude of the read signal 310 to a signal threshold, andtriggers the detection of the plurality of spiral sync marks and aplurality of spiral bursts when the magnitude of the read signalcompares favorably to the signal threshold. In this fashion, the spiraldetection module waits until a signal of sufficiently high signalstrength is detected to ignore spurious signals that may occur in theblank regions between the servo spirals and to only begin detectionafter the magnitude of the read signal 310 indicates that a “good”signal is present. In an embodiment, the magnitude of the read signalsis envelope detected, peak detected, averaged and/or filtered, such asby lowpass filtering, prior to the comparison to avoid triggering ontransient signals, impulsive noise, or other anomalous behavior that isnot indicative of the reading of a servo spiral.

Spiral detection module 250 detects the plurality of spiral sync marksbased on the detection of peaks in the read signal. In particular, thespiral detection module 250 upsamples the read signal 310 to forminterpolated read samples and detects the plurality of spiral sync marksbased on the detection of peaks in the interpolated read samples. Theinterpolation and peak detection used in this method of detecting spiralsync marks, provides an approach that is relatively insensitive to thevariations in frequency that are likely present, and also lends itselfto methods for determining the magnitude of the spirals bursts describedbelow, however, other methods including the use of bandpass filters,matched filters, integrators, and correlators, etc. can likewise beemployed to detect a spiral sync mark in the read signal 310.

In an embodiment of the present invention, spiral detection modulegenerates a timing reference signal based on the timing of one of theplurality of spiral sync marks. While any of the spiral sync marks, suchas the first spiral sync mark, SSM 322, or the last spiral sync mark,SSM 326 could be used for this purpose, the centermost one of theplurality of spiral sync marks, in this case SSM 324, makes a desirablereference point. In particular, the location of the SSM 324 near thecenter of envelope 330 means that the read signal corresponding to SSM324 has a higher magnitude and, presumably can be detected with agreater reliability than other spiral sync marks.

The timing reference signal, potentially in conjunction with the timingreference signals generated by reading subsequent traversals of otherservo spirals, can be used to control the frequency of internal readwrite operations, such as to control the locking of a disk locked clockthat is used for this purpose, and/or to trigger or adjust the timing ofother events such as read gate signals, write gate signals, etc. Inparticular, if the servo wedges to be written on the disk are spaced ina predetermined relationship to the servo spirals, the timing referencesignal can be used in place of the servo address marks for timing,before the servo wedges are written. For instance, if the servo wedgesto written on the disk are spaced in a predetermined relationship to theservo spirals such as one wedge to every two spirals, the timingreference signal from every other servo spiral can be used in place of aservo address mark that occurs once per servo wedge to generate anequivalent timing reference.

The spiral detection module 250 can also generate position error signal260 in several ways. In an embodiment of the present invention, thespiral detection module 250 identifies a centermost one of the pluralityof spiral sync marks and generates the position error signal 260 basedon a magnitude of a first of the plurality of spiral bursts thatprecedes the centermost one of the plurality of spiral sync marks and amagnitude of a second of the plurality of spiral bursts that succeedsthe centermost one of the plurality of spiral sync marks. Consideringthe example read signal 310 presented in FIG. 6, the centermost spiralsync mark 324 can be determined based on either the spiral sync markhaving a highest magnitude, or a the spiral sync mark closest to thecenter of the envelope 330, determined, for instance, based on timeperiod that the magnitude of the read signal compares favorably to thesignal threshold discussed above. The relative magnitudes of servo burst334 and servo burst 336 can be compared and/or otherwise used todetermine position error signal 260. In an embodiment of the presentinvention, spiral detection module 250 integrates the magnitude of thefirst of the plurality of spiral bursts to generate a first integratedburst magnitude and integrates the magnitude of the second of theplurality of spiral bursts to generate a second integrated burstmagnitude and that generates the position error signal based on thedifference between the first integrated burst magnitude and the secondintegrated burst magnitude. In terms of the example read signal 310 ofFIG. 6, the magnitude of the servo bursts 334 and 336 are eachintegrated over the corresponding burst duration to generate anintegrated burst magnitude for each burst, and subtracted to generate aposition error signal. In this case, the integrated magnitude servoburst 334 is greater than the integrated magnitude of servo burst 336indicating a skew in the diamond pattern and a corresponding positionerror.

As discussed above, other methods for determining position error arelikewise possible. The method described above can be modified toconsider the integrated magnitude of 2 or more spiral bursts on eitherside of the centermost SSM. Further, the offset of the centermost SSMfrom the peak of the magnitude envelope, such as envelope 330, can beused to estimate position error. In a further embodiment, spiraldetection module 250 integrates the magnitude of each of the pluralityspiral bursts to form a burst magnitude integration, identifies a spiralburst centroid based on the burst magnitude integration, and thatgenerates the position error signal based on a position of the spiralburst centroid, in relation to the beginning and ending of the diamondpattern as determined based on the period of time that the read signalmagnitude compares favorably to the signal threshold.

FIG. 7 presents a graphical diagram representation of a burst marktiming window 340 and spiral sync mark timing window 342 in accordancewith an embodiment of the present invention. After spiral detectionmodule 250 detects the first spiral sync mark, it can simplify itsdetection of subsequent spiral sync marks in the same diamond patternand the duration of intervening spiral bursts, based on a windowingtechnique. In particular, spiral detection module 250 detects theplurality of spiral sync marks by detecting a first of the plurality ofspiral sync marks 338, generating a spiral sync mark timing window, suchas SSM timing window 342, that corresponds to the estimated timing of asubsequent one of the plurality of spiral sync marks, and the detectionof the subsequent one of the plurality of spiral sync marks within thespiral sync mark timing window. This estimated timing window can bebroadened to encompass one or more additional cycles of the spiral syncmark to be detected to help compensate for variations in frequency priorto frequency lock. Similarly, spiral detection module 250 can detect theplurality of spiral bursts by detecting one of the plurality of spiralsync marks, generating a spiral burst timing window, such as spiralburst timing window 340, that corresponds to the estimated timing of asubsequent spiral burst of the plurality of spiral bursts, and thedetection of the subsequent one of the plurality of spiral bursts withinthe spiral burst timing window. It should be noted that the beginning,ending, center or other consistently defined point in a spiral syncmark, such as spiral sync mark 338, can be used to generate the timingof spiral burst timing window 340 and spiral sync mark timing window342.

FIG. 8 presents a block diagram representation of a spiral sync markdetector 142 in accordance with an embodiment of the present inventionthat can be used, in the implementation of spiral detection module 250,for generating timing reference signals such as SSM detection signal 320and magnitude estimation signals such as magnitude estimation signal318, that are used in determining timing and the position of the readhead. Broadly speaking, the spiral sync mark detector 142 operates byinterpolating the read signal 310, tracking the peaks in the signal,slicing the detected peaks into binary values, (such as assigningpositive peaks as binary 1, and negative peaks as binary 0), andcomparing the generated pattern to the spiral sync mark binary patternthat was used to generate SSM detection signal 320 when a spiral syncmark is detected. In particular, spiral sync mark detector 142 includesan upsampling module 300 that generates a plurality of upsampled readsamples by upsampling a discrete-time read signal by an upsamplingfactor. Considering the read signal 310 as a discrete time signal f(k),the upsampled read samples 312 can be represented as g(n) where:g(n)=f(n/L), if n/L is an integer, and otherwise g(n)=0. In anembodiment of the present invention, an integer upsampling factor L isused, such as L=4, 6, 8, 12, 16, . . . however, other values of Lincluding integer values can likewise be employed.

Interpolation filter module 302 generates a plurality of interpolatedread samples 314 from the upsampled read samples 312. In an embodimentof the present invention, the interpolation filter 302 is an idealfilter has an impulse response that is a finite sinc (sin(x)/x)function, however, other interpolation filters including non-idealfilters can likewise be used within the broad scope of the presentinvention.

Peak detection module 304 identifies a plurality of peak samples 316from the plurality of interpolated read samples 316. This can beaccomplished in different ways, as will be described further inconjunction with FIG. 9. For instance, the peak detection module 304 canbegin by identifying one of the plurality of peak samples 316 bycomparing the magnitude of successive ones of the plurality of filteredsamples 314. Once a peak is found, the peak detection module 304 canlook for the next peak around the sample that is L samples away.However, given an offset in frequencies between the actual and idealread frequencies, this next peak, that may be have a positive ornegative value, may be one or more neighboring samples away. Again,comparing the magnitude of the sample with j neighboring samples (forinstance, j=2, 3, 4, 6, . . . ), can determine the position of the nextpeak, and so on.

Slicer/comparison module 308 performs the functions of slicing the peaksand detecting the pattern indicative of the spiral sync mark. Inparticular, the peak samples 316 are sliced into binary decoded bitsthat are compared with the special pattern, used to generate the spiralsync marks. Slicer/comparison module 308 compares these patterns on abit by bit basis and generates a count that represents the number ofbits that match. When the number of bits matching the special patterncompare favorably to a comparison threshold, slicer/comparison module308 determines that the special pattern has been found in the sequenceof decoded bits and asserts the SSM detection signal 320.

Magnitude estimation module 306 generates a magnitude estimation signal318 from the plurality of peak samples 316. In an embodiment of thepresent invention, magnitude estimation module 306 convolves theplurality of peak samples 316 by a sequence of alternating polarity (1,−1, 1, −1, etc.) and calculates the absolute magnitude of the result togenerate magnitude estimation signal 318. In particular, the signs ofalternating peaks are inverted and summed over a window of W successivepeak samples 316 (where W=2, 3, 4, 6, 8, 12, or 16, etc., either aninteger power of two or other integer). In the event that the spiralburst signal is present, the peaks alternate. Convolving the peaks bythe alternating polarity sequence causes the magnitude of the samples toadd constructively. Taking the absolute magnitude of this sum yields amagnitude estimation signal 318 that is a relatively large positivenumber in response to a spiral burst signal being read and a smallernumber in response to other signals such as noise, other data, etc.being read. For each new peak sample 316, the detection window ofdetection estimation module 306 moves to encompass the newest peaksample 316 and to eliminate the oldest peak sample 316. In response, anupdated decoded binary bit pattern is generated and the magnitudeestimation signal 318 is updated.

FIG. 9 presents a graphical representation of the operation of peakdetection module 304 in accordance with an embodiment of the presentinvention. In particular, an example is presented that represents aneighborhood of four interpolated read samples 314 as samples {S(n),S(n+1), S(n+2) and S(n+3)}. It should be noted that the magnitudes ofneighboring samples can be compared in different ways to determine thata particular sample corresponds to a peak. In particular, the pluralityof neighboring samples {S(n), S(n+1), S(n+2) and S(n+3)} can be comparedto identify the sample 330 (in this case S(n+2)) with the greatestabsolute magnitude. In the alternative, peak detection module 304 canidentify peak samples by calculating a plurality of successive gradientsand detecting an inversion in the polarity between two successivegradients of the plurality of successive gradients. In this case, thefirst gradient S(n+1)−S(n) is positive, and S(n+2)−S(n+1) is alsopositive. However, S(n+3)−S(n+2) is negative, indicating the passage ofthe peak along the interval between [(n+3), (n+1)]. In this circumstancethe peak 330 can be estimated by the intermediate value, S(n+2).

FIG. 10 presents a graphical representation of the operation ofmagnitude estimation module 306 in accordance with an embodiment of thepresent invention. In particular, an example is presented thatrepresents a plurality of interpolated read samples 314 as S(y) withy=1, 2, 3 . . . 24, expressly shown with an upsampling factor L=4. Inthis illustration, peak detection module 304 has identified interpolatedread samples 314 represented by S(2), S(6), S(10), S(14), S(18) andS(22) as corresponding to peak samples 316. Magnitude estimation module306 inverts the sign of every other one of the peak samples 316, in thiscase S(6), S(14) and S(22), to form the values P(m), m=y/L for integervalues. In this example, magnitude estimation module 306 forms magnitudeestimation signal 318 with a sliding window that calculates the sum ofthe four preceding values of P(m).

It should be noted, that while spiral sync mark detector 142 has beendescribed in terms of the assertion of spiral sync mark detection signal320, the upsampling module 300, interpolation filter module 302, peakdetection module 304 and magnitude estimation module 306, with theappropriate choice of summing window 350, can likewise be used tointegrate the magnitude of a spiral burst for the purposes of generatinga position error signal as described above.

FIG. 11 presents a block diagram representation of a timing generator110 in accordance with an embodiment of the present invention. Inparticular a timing generator 110 is presented that can includecomponents of the read/write channel 140, disk formatter 125 and/orservo formatter 120. Timing generator 110 includes a referenceoscillator 112, such as a crystal oscillator circuit with an on-boardcrystal or a crystal that is external to timing generator 110, forgenerating a reference oscillation 113. Disk locked clock 114 providesat least one clock signal 126, such as a data frequency clock or a servofrequency clock. In particular, the clock signal 126 is locked in phaseand/or frequency with the timing reference signal 262 (during the selfservo write mode), or from detected servo address marks via servoaddress mark (SAM) detection signal 128 (after the servo wedges havebeen written to the disk) so as to provide a substantially constantnumber of clock cycles between successive servo address marks. In anembodiment of the present invention, disk locked clock 114 includes aphase-locked loop (PLL) circuit that uses the phase error between adivided reference signal and either the timing reference signal 262 or aservo address mark detection signal 128 (after the servo wedges arewritten and when a servo address mark is detected) to adjust the phaseor frequency in a closed loop control configuration.

Clock signal 126 and either timing reference signal 262 or SAM detectionsignal 128 (again depending on whether the disk controller is operatingin a self servo write mode prior to the servo wedges being completelywritten, or in a normal mode of operation after the servo wedges arepresent) are used by media event timer 125 to produce media eventssignal 124, to trigger one or more media events. In an embodiment of thepresent invention, media events signal 124 provides the start times ofone or more events such as a write event, a read event, timing event,and a servo control event that can be part of a read operation, writeoperation, servo control signal and other signal such as control signalused for timing or triggering the operation of the disk controller 130.These events can be part of a formatting of disk drive unit 100 duringinitial formatting as part of the factory setup and initialization ofthe drive, during subsequent formatting operations of disk drive unit100 and during other use of disk drive 100 in normal operation. Thestart times of these events, since they are correlated to specificlocations on the disk 102, are more precise than if generated by aconstant frequency clock and automatically provide compensation forpossible servo spin-speed variations.

FIG. 12 presents a pictorial representation of a disk 200 having aplurality of servo wedges and a plurality of tracks in accordance withan embodiment of the present invention. In particular, disk 200, such asdisk 102, writes the servo wedges on the disk after having obtainedposition and timing lock on the servo spirals of the disk, either in athe factory when the disk drive 100 is manufactured, or during someother disk initialization, reformatting or recovery operation.Twenty-four radial servo wedges, including adjacent servo wedges 202 and206, are written on the disk 200. While the servo wedges are representedas linear, non-linear configurations including arcs can also beemployed, particularly when disk 200 is implemented in a disk drive,such as disk drive unit 100 that includes an arm 106 that is moved byactuator 108 over the surface of the disk 200 by rotation. Further,while 24 servo wedges are shown for illustration purposes, greaternumbers of servo wedges, such as two hundred or more can be employed.

Five tracks, including track 208, are shown for illustrative purposes,however, a far greater number of tracks would be employed in an actualimplementation. Each servo wedge includes a servo field associated witheach track. One or more sectors of user or control data are stored alongthe track between consecutive servo wedges. Further details regardingthe contents of a servo field are presented in conjunction with FIG. 13.

FIG. 13 presents a block diagram representation of a servo field 210 inaccordance with an embodiment of the present invention. In particular, aservo field typically begins with control data 230 that includes apreamble 212 and servo address mark 214 that allow the disk controllerto recognize the beginning of the servo field 210 and the beginning ofthe servo data 232. An index mark can optionally be included in controldata 230 in place of, or in addition to servo address mark 214 toindicate a particular servo wedge that is the first or “index” wedge foreasy decoding by the disk controller 130. Servo data 232 includes trackidentification data 216 for identifying the particular track being read,and burst data 218 for providing subtrack head alignment data thatfacilitates control to a track centerline and to facilitate track seekmovements of the read/write head, etc. Servo address mark 214 is usedfor timing generation in the disk controller 130 to time the start timefor various events, such as write operations, synchronous identificationof a servo wedge during spin-up of the disk, etc. While not shown, theservo data can also include other data including a head number for amulti-head disk drive, and a wedge number that identifies the currentwedge, etc.

FIG. 14 presents a pictorial representation of a handheld audio unit 51in accordance with an embodiment of the present invention. Inparticular, disk drive unit 100 can include a small form factor magnetichard disk whose disk 102 has a diameter 1.8″ or smaller that isincorporated into or otherwise used by handheld audio unit 51 to providegeneral storage or storage of audio content such as motion pictureexpert group (MPEG) audio layer 3 (MP3) files or Windows MediaArchitecture (WMA) files, video content such as MPEG4 files for playbackto a user, and/or any other type of information that may be stored in adigital format.

FIG. 15 presents a pictorial representation of a computer 52 inaccordance with an embodiment of the present invention. In particular,disk drive unit 100 can include a small form factor magnetic hard diskwhose disk 102 has a diameter 1.8″ or smaller, a 2.5″ or 3.5″ drive orlarger drive for applications such as enterprise storage applications.Disk drive 100 is incorporated into or otherwise used by computer 52 toprovide general purpose storage for any type of information in digitalformat. Computer 52 can be a desktop computer, or an enterprise storagedevices such a server, of a host computer that is attached to a storagearray such as a redundant array of independent disks (RAID) array,storage router, edge router, storage switch and/or storage director.

FIG. 16 presents a pictorial representation of a wireless communicationdevice 53 in accordance with an embodiment of the present invention. Inparticular, disk drive unit 100 can include a small form factor magnetichard disk whose disk 102 has a diameter 1.8″ or smaller that isincorporated into or otherwise used by wireless communication device 53to provide general storage or storage of audio content such as motionpicture expert group (MPEG) audio layer 3 (MP3) files or Windows MediaArchitecture (WMA) files, video content such as MPEG4 files, JPEG (jointphotographic expert group) files, bitmap files and files stored in othergraphics formats that may be captured by an integrated camera ordownloaded to the wireless communication device 53, emails, webpageinformation and other information downloaded from the Internet, addressbook information, and/or any other type of information that may bestored in a digital format.

In an embodiment of the present invention, wireless communication device53 is capable of communicating via a wireless telephone network such asa cellular, personal communications service (PCS), general packet radioservice (GPRS), global system for mobile communications (GSM), andintegrated digital enhanced network (iDEN) or other wirelesscommunications network capable of sending and receiving telephone calls.Further, wireless communication device 53 is capable of communicatingvia the Internet to access email, download content, access websites, andprovide steaming audio and/or video programming. In this fashion,wireless communication device 53 can place and receive telephone calls,text messages such as emails, short message service (SMS) messages,pages and other data messages that can include attachments such asdocuments, audio files, video files, images and other graphics.

FIG. 17 presents a pictorial representation of a personal digitalassistant 54 in accordance with an embodiment of the present invention.In particular, disk drive unit 100 can include a small form factormagnetic hard disk whose disk 102 has a diameter 1.8″ or smaller that isincorporated into or otherwise used by personal digital assistant 54 toprovide general storage or storage of audio content such as motionpicture expert group (MPEG) audio layer 3 (MP3) files or Windows MediaArchitecture (WMA) files, video content such as MPEG4 files, JPEG (jointphotographic expert group) files, bitmap files and files stored in othergraphics formats, emails, webpage information and other informationdownloaded from the Internet, address book information, and/or any othertype of information that may be stored in a digital format.

FIG. 18 presents a pictorial representation of a laptop computer 55 inaccordance with an embodiment of the present invention. In particular,disk drive unit 100 can include a small form factor magnetic hard diskwhose disk 102 has a diameter 1.8″ or smaller, or a 2.5″ drive. Diskdrive 100 is incorporated into or otherwise used by laptop computer 52to provide general purpose storage for any type of information indigital format.

FIG. 19 presents a flowchart representation of a method in accordancewith an embodiment of the present invention. In particular, a method ispresented that can be used in conjunction with one or more of thefeatures or functions described in association with FIGS. 1-18. In step400, a plurality of spiral sync marks and a plurality of spiral burstsare detected corresponding to one of a plurality of servo spirals from aread signal from the read/write head of a disk drive. In step 402, atiming reference signal is generated based on timing of at least one ofthe plurality of the spiral sync marks. In step 404, a position errorsignal is generated based on timing of at least one of the plurality ofspiral sync marks and a magnitude of at least one of the plurality ofspiral bursts, wherein the timing reference signal and the positionerror signal are used by the disk drive for timing and positioning inself writing initial servo wedges to the disk.

In an embodiment of the present invention, step 400 includes comparing amagnitude of the read signal to a signal threshold, and triggering thedetection of the plurality of spiral sync marks and a plurality ofspiral bursts when the magnitude of the read signal compares favorablyto the signal threshold. Step 400 can further include detecting theplurality of spiral sync marks based on the detection of peaks in theread signal, such as by upsampling the read signal to form interpolatedread samples, and detecting the plurality of spiral sync marks based onthe detection of peaks in the interpolated read samples. In addition,step 400 can include identifying a centermost one of the plurality ofspiral sync marks, and step 404 can include generating the positionerror signal based on a magnitude of a first of the plurality of spiralburst that precedes the centermost one of the plurality of spiral syncmarks and a magnitude of a second of the plurality of spiral burst thatsucceeds the centermost one of the plurality of spiral sync marks. Also,step 400 can include integrating the magnitude of the first of theplurality of spiral bursts to generate a first integrated burstmagnitude, and integrating the magnitude of the second of the pluralityof spiral bursts to generate a second integrated burst magnitude. Basedon these values, step 404 can include generating the position errorsignal based on the difference between the first integrated burstmagnitude and the second integrated burst magnitude. Step 400 can alsoinclude detecting a first of the plurality of spiral sync marks,generating a spiral sync mark timing window that corresponds to theestimated timing of a subsequent one of the plurality of spiral syncmarks, detecting the subsequent one of the plurality of spiral syncmarks within the spiral sync mark timing window Likewise, step 400 caninclude generating a spiral burst timing window that corresponds to theestimated timing of a subsequent spiral burst of the plurality of spiralbursts, based on a detected spiral sync mark, and detecting thesubsequent one of the plurality of spiral bursts within the spiral bursttiming window.

In an embodiment, step 402 includes identifying a centermost one of theplurality of spiral sync marks, and generating a timing reference signalbased on timing of the centermost one of the plurality of spiral syncmarks. Alternatively, step 400 integrating a magnitude of the pluralityspiral bursts to form a burst magnitude integration, identifying aspiral burst centroid based on the burst magnitude integration, andgenerating the position error signal based on a position of the spiralburst centroid.

FIG. 20 presents a flowchart representation of a method in accordancewith an embodiment of the present invention. A method is presented thatcan be used in conjunction with one or more of the features or functionsdescribed in association with FIGS. 1-19. In particular, this methodincludes several steps common to the method of FIG. 19 that are referredto by common reference numerals. In addition, the method generates aclock signal and at least one media event trigger, based on the timingreference signal, as shown in step 406. In step 408, the position of theread/write head is controlled based on the position error signal. Instep 410, servo data is generated corresponding to a plurality of servowedges of the disk. In step 412, write signals are generated for writingthe plurality of servo wedges on the disk, based on the clock signal andthe at least one media event trigger.

While the various embodiments described herein focus primarily on thedetection of bipolar sinusoidal read signals that result from thereading of a servo spiral such as servo spiral 160, unipolar sinusoidalsignals, possibly used in conjunction with PMR, can likewise be detectedby AC coupling these signals to create a bipolar signal, or by othermodifications.

Further, while the various embodiments described herein describeupsampling and interpolating a discrete-time read signal, alternativelythe present invention can operate by oversampling a read signal at asampling frequency that is a multiple M above a Nyquist sampling rate ofthe read signal, where M is either an integer or a fraction. In thisfashion, the peak detection, such as by peak detection module 304,identifies the peaks in this oversampled read signal, rather than frominterpolated read samples.

While the present invention has been described in terms of a magneticdisk, other nonmagnetic storage devices including optical disk drivesincluding compact disks (CD) drives such as CD-R and CD-RW, digitalvideo disk (DVD) drives such as DVD-R, DVD+R, DVD-RW, DVD+RW, etc canlikewise be implemented in accordance with the functions and features ofthe presented invention described herein.

As one of ordinary skill in the art will appreciate, the term“substantially” or “approximately”, as may be used herein, provides anindustry-accepted tolerance to its corresponding term and/or relativitybetween items. Such an industry-accepted tolerance ranges from less thanone percent to twenty percent and corresponds to, but is not limited to,component values, integrated circuit process variations, temperaturevariations, rise and fall times, and/or thermal noise. Such relativitybetween items ranges from a difference of a few percent to magnitudedifferences. As one of ordinary skill in the art will furtherappreciate, the term “operably coupled”, as may be used herein, includesdirect coupling and indirect coupling via another component, element,circuit, or module where, for indirect coupling, the interveningcomponent, element, circuit, or module does not modify the informationof a signal but may adjust its current level, voltage level, and/orpower level. As one of ordinary skill in the art will also appreciate,inferred coupling (i.e., where one element is coupled to another elementby inference) includes direct and indirect coupling between two elementsin the same manner as “operably coupled”. As one of ordinary skill inthe art will further appreciate, the term “compares favorably”, as maybe used herein, indicates that a comparison between two or moreelements, items, signals, etc., provides a desired relationship. Forexample, when the desired relationship is that signal 1 has a greatermagnitude than signal 2, a favorable comparison may be achieved when themagnitude of signal 1 is greater than that of signal 2 or when themagnitude of signal 2 is less than that of signal 1.

The various circuit components can be implemented using 0.35 micron orsmaller CMOS technology. Provided however that other circuittechnologies, both integrated or non-integrated, may be used within thebroad scope of the present invention. Likewise, various embodimentsdescribed herein can also be implemented as software programs running ona computer processor. It should also be noted that the softwareimplementations of the present invention can be stored on a tangiblestorage medium such as a magnetic or optical disk, read-only memory orrandom access memory and also be produced as an article of manufacture.

Thus, there has been described herein an apparatus and method, as wellas several embodiments including a preferred embodiment, forimplementing a self servo writing disk controller. Various embodimentsof the present invention herein-described have features that distinguishthe present invention from the prior art.

It will be apparent to those skilled in the art that the disclosedinvention may be modified in numerous ways and may assume manyembodiments other than the preferred forms specifically set out anddescribed above. Accordingly, it is intended by the appended claims tocover all modifications of the invention which fall within the truespirit and scope of the invention.

1. A disk controller for use in a self servo writing disk drive havingat least one read/write head for writing servo data to a disk in a servowrite mode and for reading and writing user data in a user mode, thedisk controller comprising: a spiral detection module that analyzes aread signal from the read/write head, detects a plurality of spiral syncmarks and a plurality of spiral bursts corresponding to one of aplurality of servo spirals written on the disk, and that generates atiming reference signal based on timing of at least one of the pluralityof the spiral sync marks and a position error signal based on timing ofat least one of the plurality of spiral sync marks and a magnitude of atleast one of the plurality of spiral bursts; a timing generator,operably coupled to the spiral detection module, for generating a clocksignal and for generating at least one media event trigger that is basedon the timing reference signal; a device controller, operably coupled tothe spiral detection module, for controlling at least one drive devicebased on the position error signal; a servo data generation module thatgenerates the servo data corresponding to a plurality of servo wedges ofthe disk; and a servo write module, operably coupled to the servo datageneration module and the timing generator, that generates write signalsfor writing the plurality of servo wedges on the disk based on the clocksignal and the at least one media event trigger.
 2. The disk controllerof claim 1 wherein the spiral detection module compares a magnitude ofthe read signal to a signal threshold, and wherein spiral detectionmodule triggers the detection of the plurality of spiral sync marks anda plurality of spiral bursts when the magnitude of the read signalcompares favorably to the signal threshold and a decoded binary patternmatches a predefined pattern.
 3. The disk controller of claim 1 whereinthe spiral detection module detects the plurality of spiral sync marksbased on the detection of peaks in the read signal.
 4. The diskcontroller of claim 1 wherein the spiral detection module upsamples theread signal to form interpolated read samples and that detects theplurality of spiral sync marks based on the detection of peaks in theinterpolated read samples.
 5. The disk controller of claim 1 wherein thespiral detection module detects the plurality of spiral sync marks bydetecting a first of the plurality of spiral sync marks, generating aspiral sync mark timing window that corresponds to the estimated timingof a subsequent one of the plurality of spiral sync marks, and thedetection of the subsequent one of the plurality of spiral sync markswithin the spiral sync mark timing window.
 6. The disk controller ofclaim 1 wherein the spiral detection module detects the plurality ofspiral bursts by detecting one of the plurality of spiral sync marks,generating a spiral burst timing window that corresponds to theestimated timing of a subsequent spiral burst of the plurality of spiralbursts, and the detection of the subsequent one of the plurality ofspiral bursts within the spiral burst timing window.
 7. The diskcontroller of claim 1 wherein the spiral detection module identifies acentermost one of the plurality of spiral sync marks and that generatesthe position error signal based on a magnitude of a first of theplurality of spiral burst that precedes the centermost one of theplurality of spiral sync marks and a magnitude of a second of theplurality of spiral burst that succeeds the centermost one of theplurality of spiral sync marks.
 8. The disk controller of claim 7wherein the spiral detection module integrates the magnitude of thefirst of the plurality of spiral burst to generate a first integratedburst magnitude and integrates the magnitude of the second of theplurality of spiral bursts to generate a second integrated burstmagnitude and that generates the position error signal based on thedifference between the first integrated burst magnitude and the secondintegrated burst magnitude.
 9. The disk controller of claim 1 whereinthe spiral detection module integrates a magnitude of the pluralityspiral bursts to form a burst magnitude integration, identifies a spiralburst centroid based on the burst magnitude integration, and thatgenerates the position error signal based on a position of the spiralburst centroid.
 10. The disk controller of claim 1 wherein the spiraldetection module identifies a centermost one of the plurality of spiralsync marks and generates a timing reference signal based on timing ofthe centermost one of the plurality of spiral sync marks.
 11. A methodfor use in a disk drive having at least one read/write head for writingservo data to a disk in a servo write mode and for reading and writinguser data in a user mode, the method comprising: detecting a pluralityof spiral sync marks and a plurality of spiral bursts corresponding toone of a plurality of servo spirals from a read signal from theread/write head; generating a timing reference signal based on timing ofat least one of the plurality of the spiral sync marks; generating aposition error signal based on timing of at least one of the pluralityof spiral sync marks and a magnitude of at least one of the plurality ofspiral bursts; wherein the timing reference signal and the positionerror signal are used by the disk drive for timing and positioning inself writing initial servo wedges to the disk.
 12. The method of claim11 wherein the step of detecting a plurality of spiral sync marks and aplurality of spiral bursts includes: comparing a magnitude of the readsignal to a signal threshold; and triggering the detection of theplurality of spiral sync marks and a plurality of spiral bursts when themagnitude of the read signal compares favorably to the signal threshold.13. The method of claim 11 wherein the step of detecting a plurality ofspiral sync marks and a plurality of spiral bursts includes: upsamplingthe read signal to form interpolated read samples; and detecting theplurality of spiral sync marks based on the detection of peaks in theinterpolated read samples.
 14. The method of claim 11 wherein the stepof generating a timing reference signal includes: identifying acentermost one of the plurality of spiral sync marks; and generating atiming reference signal based on timing of the centermost one of theplurality of spiral sync marks.
 15. The method of claim 11 wherein thestep of detecting a plurality of spiral sync marks and a plurality ofspiral bursts includes: identifying a centermost one of the plurality ofspiral sync marks; wherein the step of generating the position errorsignal generates the position error signal based on a magnitude of afirst of the plurality of spiral burst that precedes the centermost oneof the plurality of spiral sync marks and a magnitude of a second of theplurality of spiral burst that succeeds the centermost one of theplurality of spiral sync marks.
 16. The method of claim 15 wherein thestep of detecting a plurality of spiral sync marks and a plurality ofspiral bursts includes: integrating the magnitude of the first of theplurality of spiral burst to generate a first integrated burstmagnitude; and integrating the magnitude of the second of the pluralityof spiral bursts to generate a second integrated burst magnitude;wherein the step of generating the position error signal generates theposition error signal based on the difference between the firstintegrated burst magnitude and the second integrated burst magnitude.